| 摘要 |
A differential line driver having integrated output termination resistors is disclosed. The termination resistors are a combination of a controlled transistor and a low precision resistor. The transistor calibrates-out the imprecision of the resistor based on a precise electrical reference. In a preferred embodiment the transistor is a CMOS transistor and the resistor is a CMOS resistor. The combination of a CMOS transistor and CMOS resistor features higher linearity and precision than a CMOS transistor alone due to the smaller effective drain-source voltage across the CMOS transistor. Moreover, the present invention discloses independent programmability of the integrated output termination resistor, the output common mode voltage, and the output amplitude. The value of the output termination resistor(s), the value of the output common mode voltage, and the value of the output amplitude are controlled independently and are continuously maintained with respect to a precise electrical reference. As a result, the value of the output termination resistance, the value of the output common mode voltage, and the value of the output amplitude are insensitive to manufacturing process tolerances and variations in temperature and supply voltage. |
